Maybe one for Steamship (or members who had LPG on other vehicles; this is a generic post).

Over the past few days the car has "fallen off the gas" in the middle of journeys , not under hard acceleration. After pulling over it went straight back onto gas first few times but now is struggling to find the gas again.

Hi it could be starving it causing a low gas pressure to switch back to petrol. as well as the filters that need changing periodically. the solenoids being magnetic collect all the rust and iron filings out of the storage tanks and your gas tank. the reducer can stop working properly from heavy ends gumming it up. so if you've done a lot of miles it could just need a service. by a specalist or yourself if your competent the LPG forums are very helpful. this is what i found in mine.
Dave

Depends on the engine. I had a lexus rx300 converted to lpg and my dad had his Mazda tribute done at the same time. The Mazda Tribute ( Ford ) burnt through its valves in about a year and 15k miles. My Lexus is still going strong. It was converted at 36k miles about 10 years ago and my dad still runs it on lpg today at about 150k miles. The lexus has never had anything apart from the routine stuff.